1. Field of the Invention
The present invention relates to a shaft seal device, and more particularly to a shaft seal device for use in a bearing unit such as a plummer block used in iron and steel equipment and the like.
2. Prior Art
A conventional shaft seal device of a bearing unit used in iron and steel equipment and the like, such as an oil seal, requires applying lubricant to sliding parts (lips) thereof. To this end, in steel works, usually an operation of supplying lubricant to lips of oil seals is periodically carried out, which costs time and labor. Further, the conventional shaft seal device has a problem that excess lubricant leaking from lips of oil seals splashes with rotation of the rotary shaft to contaminate or stain its environment, rolled plates produced, etc. To solve this problem, a shaft seal device as shown in FIG. 13 has been proposed by Japanese Laid-Open Utility Model Publication (Kokai) No. 6-32837.
The proposed shaft seal device 101 is comprised of a pair of core metal members 102 and 103 with fitting collars 109 and 110 integrally fitted one upon another, and seal members 104 and 105 mounted on inner peripheral edges of main bodies 107 and 108 of the core metal members 102, 103. The seal members 104, 105 have flexible lips which are suitably deflected and urged against an outer peripheral surface of a rotary shaft 111 to be sealed, in operation. A clip 115 is fitted on an outer peripheral surface of the lip of the seal member 105 so as to obtain a sufficient urging force of the lip. A lubricant-bearing polymer which is so-called xe2x80x9cplastic greasexe2x80x9d 106xe2x80x3 is filled in a gap between the opposed main bodies 107, 108 of the core metal members 102, 103.
Lubricant continuously exudes or oozes from the lubricant-bearing polymer contained in the oil seal is led to the lips of the seal members 104, 105 to lubricate the same. This can dispense with the periodical operation of supplying lubricant to the lips. Besides, the amount of lubricant exuding from the polymer is so small as to solve the above-mentioned problem of environmental contamination.
According to the conventional arrangement, however, since the exudation amount of lubricant is very small, a sufficient amount of lubricant cannot reach the lips of the seal members 104, 105. Further, even if the exudation amount of lubricant is sufficient, the lubricant flows along the inner peripheral portion of the lubricant-bearing polymer and stays at the lowermost inner peripheral portion of the polymer but does not reach the lips.
It is therefore an object of the present invention to provide a shaft seal device which is capable of sealing a rotary shaft in a positive and reliable manner without requiring a periodical lubricant-supplying operation, and is free from contamination of its environment, products, etc. by splashing of excess lubricant leaking from the oil seal lip.
To attain the above object, the present invention provides a shaft seal device for a bearing unit having a bearing fitted on a rotary shaft, and a housing accommodating the rotary shaft extending therethrough, the housing having opposite ends, comprising:
an annular sealing channel formed in at least one of the opposite ends of the housing, the annular sealing channel having opposite lateral wall surfaces; and
an annular lubricant-bearing polymer member accommodated in the annular sealing channel and fitted on the rotary shaft, the polymer member having opposite end surfaces, and an outer peripheral portion;
wherein the polymer member has an inside diameter substantially equal to an outer diameter of the rotary shaft at an initial stage of rotation of the rotary shaft; and
wherein at least part of the opposite end surfaces or the outer peripheral portion of the polymer member is disposed substantially in contact with the opposite lateral wall surfaces of the annular sealing channel.
With the above arrangement, at an initial stage of rotation of the rotary shaft, the inside diameter of the annular lubricant-bearing polymer member is substantially equal to the outer diameter of the rotary shaft so that the polymer member closely contacts the rotary shaft at its inner peripheral surface or is rotated by the rotating rotary shaft while sliding thereon, while at the same time at least part of the opposite end surfaces or the outer peripheral portion of the polymer member substantially contacts the opposite lateral wall surfaces of the sealing channel. As a result, the surfaces of the polymer member in contact with its counterpart function as sealing surfaces to prevent dust and splashed water droplets from entering the bearing unit from the outside of the housing.
The lubricant-bearing polymer member has a function of exuding lubricant from its surfaces and has a nature that its inside diameter and outside diameter become reduced depending upon the exudation amount of lubricant. Therefore, when the inside diameter of the polymer member which initially closely contacts the rotary shaft or slides thereon becomes smaller than the outside diameter of the rotary shaft with exudation of the lubricant from the polymer member as the rotation of the rotary shaft continues, the polymer member becomes tightly fitted on the rotary shaft, whereby the former rotates together with the latter. Thereafter, the rotation of the polymer member is maintained with at least part of the opposite end surfaces or the outer peripheral portion of the polymer member in sliding contact with the opposite lateral wall surfaces of the sealing channel, or the polymer member rotates with delay relative to the rotation of the rotary shaft due to the sliding resistance of the sliding surfaces between the polymer member and the sealing channel. As a result, the surfaces of the polymer member in contact with its counterpart function as sealing surfaces to prevent dust and splashed water droplets from entering the bearing unit from the outside of the housing, as is the case with the initial stage of rotation of the rotary shaft.
In other words, the shaft seal device assumes an initial state in which the inside diameter of the lubricant-bearing polymer member is substantially equal to the outside diameter of the rotary shaft, and a state in which the inside diameter of the polymer member is smaller than the outside diameter of the rotary shaft such that the polymer member is tightly fitted on the rotary shaft. Between the two states, however, no change occurs in the position of the sealing surfaces, though the state of the sealing surfaces changes, and in the both states, it is possible to dust and splashed water droplets from entering the bearing unit.
Further, since the lubricant continuously exudes from the sliding surfaces of the lubricant-bearing polymer member to well lubricate the sliding surfaces, which prevents wear of the polymer member due to the friction between the polymer member and its counterpart as well as formation of a gap between the two members, whereby dust and splashed water droplets can be prevented from entering the bearing unit. The lubricant can exude from the polymer member over a long time, making it unnecessary to periodically supply lubricant. Besides, the exudation amount of lubricant is very small but equal to the minimum amount required for lubrication such that the exuded lubricant will not be splashed with rotation of the rotary shaft, and therefore the environment and the products cannot be contaminated by the lubricant.
Preferably, the shaft seal device according to the present invention includes an annular covering member formed of an elastic material with an inner peripheral channel formed therein. The annular covering member is fitted in the annular sealing channel in an elastically compressed fashion, and the lubricant-bearing polymer member is accommodated in the inner peripheral channel of the covering member. With this arrangement, the lubricant-bearing polymer member will not directly slide on the associated end portion of the housing but slides on the covering member. As a result, the possibility of wearing of the polymer member is reduced.
Preferred forms of the present invention are as follows:
1. At least one of the opposite lateral wall surfaces of the annular sealing channel is tapered, and at least one of opposite outer end surfaces of the covering member is tapered according to the tapered at least one of the opposite lateral walls of the sealing channel.
2. The covering member has opposite inner end surfaces, at least one of which is roughened.
3. The covering member has opposite end walls, at least one of which has at least one through hole formed therein.
4. The opposite end surfaces of the lubricant-bearing polymer member are spaced from respective associated ones of the opposite inner end surfaces of the covering member with a gap formed therebetween, the gap extending along one of the opposite end surfaces of the polymer member, an outer peripheral surface thereof, and the other end surface thereof so as to present a form of a labyrinth, and lubricant exuding from the polymer member is filled in the gap.
5. A plurality of circumferentially extending protuberances are formed on at least one of the opposite end surfaces of the lubricant-bearing polymer member and the opposite inner end surfaces of the covering member.
6. The outer peripheral portion of the lubricant-bearing polymer member is formed therein with a plurality of circumferentially extending grooves, while an inner peripheral surface of the covering member has formed thereon a plurality of circumferentially extending protuberances at locations corresponding respectively to the circumferentially extending grooves of the lubricant-bearing polymer member, the protuberances being inserted in respective associates ones of the circumferentially extending grooves. In this case, more preferably, the opposite end surfaces of the lubricant-bearing polymer member are spaced from the opposite inner end surfaces of the covering member so as to present a gap in the form of a labyrinth between the two members.
7. An inner peripheral portion of the lubricant-bearing polymer member has formed thereon at least one lip disposed for sliding contact with the rotary shaft, a part of the inner peripheral portion other than a part thereof formed with the at least one lip has an inside diameter larger than the outside diameter of the rotary shaft.
8. At least one of the outer peripheral portion of the lubricant-bearing polymer member and an inner peripheral portion of the covering member has at least one lip formed thereon, the at least one lip being disposed in elastic contact with an inner peripheral surface of the covering member or the outer peripheral surface of the polymer member. In this case, more preferably, the at least one lip is formed on the outer peripheral portion of the lubricant-bearing polymer member and projects from an associated one of the opposite end surfaces of the polymer member in a longitudinal direction of the rotary shaft. Alternatively, the at least one lip entirely may lie in the range of the thickness of the polymer member such that the end surfaces of the polymer member and the inner end surfaces of the covering member are in contact with each other.
9. At least one of at least one of the opposite end surfaces of the lubricant-bearing polymer member and at least one of opposite inner end surfaces of the covering member has at least one lip formed thereon, the at least one lip being each disposed in elastic contact with an associated one of the opposite end surfaces of the polymer member or an associated one of the opposite inner end surfaces of the covering member.
10. The outer peripheral portion of the lubricant-bearing polymer member has a plurality of circumferentially extending grooves formed therein, while an inner peripheral surface of the covering member has formed thereon a plurality of circumferentially extending protuberances at locations corresponding respectively to the circumferentially extending grooves of the lubricant-bearing polymer member, the protuberances being inserted in respective associates ones of the circumferentially extending grooves, and further, at least one of at least one of the opposite end surfaces of the lubricant-bearing polymer member and at least one of opposite inner end surfaces of the covering member has at least one lip formed thereon, the at least one lip being each disposed in elastic contact with an associated one of the opposite end surfaces of the polymer member or an associated one of the opposite inner end surfaces of the covering member.
11. The outer peripheral portion of the covering member has a circumferentially extending outer peripheral groove formed therein, the covering member having formed therein a plurality of through holes for supply of lubricant circumferentially arranged and extending from the outer peripheral groove to the inner peripheral surface of the covering member, and the housing of the bearing unit has formed therein a port for supply of lubricant upwardly extending from an uppermost position of the outer peripheral groove.
A description will be made of the chemical composition of a lubricant-bearing polymer that forms the lubricant-bearing polymer member used in the bearing unit employing the shaft seal device according to the present invention hereinbelow.
The lubricant-bearing polymer consists essentially of a polyolefine resin, and a lubricant such as a paraffin mineral oil and grease. The polymer may be produced by heating a raw material prepared from a mixture of the polyolefine resin and the lubricant to a temperature above its melting point into a plastic state, and then cooling the same into a solid state. Alternatively, the lubricant-bearing polymer may be polyurethane rubber which has been hardened with grease contained therein, or may be produced from a material consisting essentially of a polyester elastomer resin, and a lubricant such as ester oil and ester oil-base grease by heating a raw material prepared from a mixture of the polyester elastomer resin and the lubricant to a temperature above its melting point into a plastic state, and then cooling the same into a solid state. The possible chemical composition of the polymer is 10-50 weight % the resin or the rubber, and 90-50 weight % the lubricant. Since the strength required for the polymer member to serve as a structural member is lower as the content of the resin or the rubber is lower, the preferable chemical composition is 20-50 weight % the resin or the rubber, and 80-50 weight % the lubricant. As the lubricant, other materials such as paraffin hydrocarbon oil, naphthene hydrocarbon oil, mineral oil, ether oil, and ester oil may be used.
The above and other objects, feature, and advantages of the invention will become more apparent from the following detailed description taken in conjunction with the accompanying drawings.